I would probably take the pivot arms off and inspect them from the inside. Its possible the bearing are rusting or falling apart and causing the squeaking. You cant really tell until you take the pivot arms off. In the event the bearings are rusting check with your dealer about replacement

The other options are to take the bike to your dealer and explain the problem to him. A skilled mechanic at a Giant shop might know right where to look.

The third option would be to just live with the squeak until you upgrade. It looks like you have all the parts to upgrade to a nice Trance. Start checking Ebay for a lightly used Trance frame.

The third option would be to just live with the squeak until you upgrade. It looks like you have all the parts to upgrade to a nice Trance. Start checking Ebay for a lightly used Trance frame.

I am using an indepent mechanic, although he's excellent especially w/mtb his current day shop is not a Giant shop (he's tight w/Jamis). The LBS I bought it is more pricey, and I think i saw a nicer Giant mtb around $3,000, the owner sad 'its a different technology.

I just upgraded my Giant Road bike from OCR-3 to TCR advanced, and bought a Trek 5600 (road) just prior to buying the Yukon FX, some I am hoping to get some wear out of this MTB. The OCR-3, I got rid out of mainly because it was too big (a large), happy the FX is medium.

Believe it or not, when I pogo on the MTB the Fox shoxs make a sound too, so the rear hinge has something to harmonize with.

here below a recent pic of the upgraded fx in the wilds of ringwood nj

If you ride in the wet then

that may have caused the rear pivots to need a regrease or even replacement as borregokid says. Also, if you ride in the wet, the discs will join in with some extra noise; you could start an orchestra!
Jim